The present invention relates generally to information processing systems and more particularly to a methodology and implementation for electromagnetic radiation protection in digital electronic systems.
Subject matter disclosed and not claimed herein is disclosed and claimed in one or more of the following related co-pending applications, which are assigned to the assignee of the present application and included herein by reference:
Attorney Docket AUS-2000-0248-US1;
Attorney Docket AUS-2000-0250-US1; and
Attorney Docket AUS-2000-0251-US1.
As the operating frequencies of digital computers continues to increase over time, the higher frequencies present scalability problems for other system elements, such as the electromagnetic shields of the input-output (I/O) subsystem and electronic packaging. Such shielding is required in order to meet electromagnetic compatibility (EMC) requirements to avoid interference with other electronic equipment. It is common practice to use the external chassis as the major radio frequency (RF) EMC shield or xe2x80x9cFaraday cagexe2x80x9d. Above 500 MHz, containment of the RF fields by such a Faraday cage at the box level becomes very difficult, since shielding at the box level becomes much more difficult at those frequencies. Further, current packaging technologies do not scale very well at all at the higher frequencies because of difficulties in providing adequate shielding at the box level for RF EMC noise isolation.
An RF Faraday cage is an electrically closed box of conducting surfaces. Where the conducting surfaces are sufficiently thicker than the electromagnetic skin depth at the RF frequency of interest so that internally generated RF fields are kept within the box. This is normally done by interconnecting the various parts of a unit""s electrically conducting exterior surfaces in order to form the equivalent of a seamlessly closed box of conducting surfaces. By necessity, these surfaces are formed by many different smaller surfaces in order to meet normal reliability, availability and serviceability (RAS) requirements. This leaves many openings of slots and holes in the conducting surfaces. For mid frequencies, these openings can be kept much smaller than the wavelength of the RF to be contained so that the RF coupling through the openings is sufficiently small. Also, for mid frequencies, the interior dimensions of a typical box are sufficiently smaller than the wavelength of the RF so that no significant resonance enhancement of the RF coupling through the openings occurs. Above 500 MHz, containment of the RF fields by such a Faraday cage at the box level becomes very difficult. This is because the shorter wavelength itself enhances the coupling through standard size holes and because at the shorter wavelength, there is so much internal resonance, that one can always be found in any frequency band that will greatly enhance the coupling through some hole or slot.
Thus there is a need for an improved methodology and implementing system which provides for improved electromagnetic radiation protection in a digital signal processing system.
A method and implementing electronic connection system are provided including a nested set of RF Faraday cages within the system with integrated circuit packages containing the core drivers and receivers as the innermost Faraday cage, with additional Faraday cages being implemented at each outward level through card, board, backplane and unit level and into the network level.